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CHAIN  GRATE 
STOKERS 


THE  BABCOCK  &  WILCOX  CO. 
NEW  YORK 


•a 


Copyright,  1914,  by 
The  Babcock  &  Wilcox  Co. 


Bartlett-Orr  Press 
New  York 


THE    BABCOCK    &   WILCOX   CO, 

85    LIBERTY    STREET,    NEW    YORK,    U.   S.   A. 


Works 

BAYONNE     .     NEW    JERSEY 
BARBERTON      .     .     .     OHIO 

Directors 

E.    H.    WELLS,    President  J.    E.    EUSTIS,    Secretary 

W.    D.    HOXIE,    ist  Fice-President  F.    G.    BOURNE 

E.    R.    STETTINIUS,    2nd  Vice-President  O.    C.    BARBER 

J.    G.    WARD,    Treasurer  C.    A.    KNIGHT 

Branch    Offices 

ATLANTA CANDLER  BUILDING 

BOSTON 35  FEDERAL  STREET 

CHICAGO MARQUETTE  BUILDING 

CINCINNATI TRACTION  BUILDING 

CLEVELAND NEW  ENGLAND  BUILDING 

DENVER 435  SEVENTEENTH  STREET 

HAVANA,  CUBA 104  CALLE  DE  AGUIAR 

HOUSTON SOUTHERN  PACIFIC  BUILDING 

LOS  ANGELES I.  N.  VAN  NUY'S  BUILDING 

NEW  ORLEANS SHUBERT  ARCADE 

PHILADELPHIA NORTH  AMERICAN  BUILDING 

PITTSBURGH FARMERS'  DEPOSIT  BANK  BUILDING 

PORTLAND,  ORE SPALDING  BUILDING 

SALT  LAKE  CITY KEARNS  BUILDING 

SAN  FRANCISCO 40  FIRST  STREET 

SEATTLE MUTUAL  LIFE  BUILDING 

TUCSON,  ARIZ SANTA  RITA  HOTEL  BUILDING 

Export  Department,  New  York:     Alberto  de  Verastegui,  Director 

TELEGRAPHIC    ADDRESS:     FOR    NEW  YORK,   "GLOVEBOXES" ; 
FOR    HAVANA,  "BABCOCK" 


435997 


\ 


VV 


AUTOMATIC  STOKERS 

ITH  the  modern  tendency  toward  increased  overloads,  high  efficien- 
cies, and  smokeless  combustion,  there  has  come  an  enormous  increase 
in  the  field  of  usefulness  for  the  automatic  stoker. 


Inasmuch  as  the  capacity  of  a  properly  designed  boiler  is  limited  almost 
entirely  by  the  amount  of  fuel  that  may  be  burned  in  its  furnace,  and  as 
combustion  rates  may  be  secured  with  an  automatic  stoker  which  cannot  be 
approached  by  ordinary  hand-firing  methods,  the  increased  capacity  to  be  obtained 
from  a  given  amount  of  heating  surface  with  a  stoker-fired  over  a  hand -fired 
furnace  is  an  obvious  advantage. 

Increased  efficiency  is  another  of  the  important  advantages  of  the  stoker- 
fired  over  the  hand-fired  boiler.  With  such  an  apparatus  it  is  possible  to  make 
use  of  a  poorer  grade  of  coal  with  an  efficiency  as  high  or  higher  than  that 
obtained  with  better  grades  of  fuel  in  hand-fired  furnaces.  Such  an  increase  in 
efficiency  is  the  result  of  the  even  and  continuous  firing  of  an  automatic  stoker 
as  against  the  intermittent  firing  of  the  hand-fired  furnace,  and  a  constant  air 
supply  as  against  variation  in  this  supply  with  the  changing  furnace  conditions 
which  cannot  be  avoided  in  hand-fired  practice.  Still  another  cause  for  the  increase 
in  efficiency  is  the  almost  complete  absence  of  the  necessity  for  working  the  fires. 
When  properly  proportioned  stokers  and  furnaces  are  operated  in  connection 
with  a  well-designed  boiler,  the  capacity  obtainable  may  be  increased  without  the 
loss  of  efficiency  at  the  higher  ratings  which  would  accompany  such  an  increase 
with  hand-fired  furnaces. 

The  labor  saving  resulting  from  the  installation  of  such  an  apparatus  is  a 
large  item  in  a  properly  designed  plant.  This  is  a  feature,  however,  that  must 
be  considered  from  several  aspects.  It  is  true  that  a  stoker  feeds  coal  to  the  fire 
automatically,  but  if  this  coal  has  to  be  fed  first  to  the  stoker  hopper  by  hand, 
much  of  its  automatic  advantage  is  lost.  This  is  also  true  of  the  handling  of  the 
ash  from  such  an  installation.  When  coal  and  ash-handling  apparatus  is  not 
installed,  there  is  no  saving  in  labor.  In  large  plants,  however,  stokers,  used  in 
conjunction  with  the  modern  methods  of  coal  storage  and  coal  and  ash  handling, 
make  possible  a  large  labor  saving.  In  small  plants  the  labor  saving  effected  by 
the  use  of  stokers  is  negligible,  while  the  expense  of  the  installation  is  no  less 
proportionately  than  in  large  plants. 

While  the  question  of  smoke  and  smokeless  combustion  is  largely  one  of 
degree,  and  certain  conditions  may  arise  under  which  any  furnace  may  cause 
smoke,  it  may  be  safely  stated  that  a  stoker-fired  plant,  under  ordinary  operating 
conditions,  is  much  more  nearly  smokeless  than  one  which  is  hand  fired.  This 
is  due  to  the  same  causes  as  are  given  above  for  the  increase  in  efficiency  possible 
with  stoker-fired  boilers  over  hand  fired,  namely,  those  features  leading  to  the 
better  combustion  that  may  be  secured  where  stokers  are  used. 


BABCOCK     &    WILCOX     CHAIN     GRATE    STOKER    INSTALLED    WITH 

BABCOCK    &    WILCOX    BOILER  — A    SETTING    WHICH    HAS    BEEN 

PARTICULARLY    SUCCESSFUL     IN     MINIMIZING    SMOKE 


Against  the  advantages  resulting  from  the  use  of  automatic  stokers  there 
are  several  features  that  must  be  considered  in  determining  the  wisdom  of  making 
such  an  installation. 

The  cost  of  stokers  is  greatly  in  excess  of  the  cost  of  hand -fired  furnaces. 
Due  to  the  higher  capacities  at  which  stoker-fired  boilers  are  ordinarily  operated, 
the  upkeep  cost  of  the  furnace  is  greater  than  in  hand-fired  practice.  This 
applies  not  only  to  the  upkeep  cost  of  the  stoker  proper,  but  also  to  that  of  the 
furnace  brickwork.  From  their  greater  first  cost  and  the  more  severe  nature  of 
the  service  that  stokers  are  required  to  meet,  the  depreciation  will  obviously  be 
greater  than  in  the  case  of  hand-fired  furnace  material. 

Automatic  stokers  require  a  higher  degree  of  intelligence  on  the  part  of 
the  operating  crew  than  do  hand-fired  furnaces,  but  such  an  objection  is  largely 
overcome  by  the  present-day  tendency  toward  the  employment  of  a  better  class  of 
labor  in  the  boiler  room.  An  early  objection  to  stokers  in  general  had  its 
basis  in  the  fact  that  the  ash  contained  an  excessive  amount  of  unburned  carbon. 
This  objection  also  has  been  largely  overcome  by  improvements  in  design  of 
practically  all  stokers. 

From  this  brief  statement  of  advantages  and  disadvantages,  it  is  obvious 
that  the  question  of  the  advisability  of  a  stoker  installation  is  one  which  must  be 
considered  most  carefully  in  all  of  its  phases.  The  added  efficiency  and  capacity, 
the  labor  saving  possible,  and  the  smokelessness  must  be  balanced  against  the 
added  first  cost  or  interest  on  the  investment,  the  depreciation  and  maintenance 
cost,  the  steam  required  for  stoker  drive  or  blast,  and  the  added  cost  of 
furnace  upkeep. 

In  general,  a  stoker  installation  will  be  found  profitable  in  the  larger  plants 
properly  equipped  for  handling  the  fuel  and  ashes.  In  small  plants  such  an 
installation  may  be  advisable  only  where  the  question  of  smokeless  combustion 
is  paramount. 


TWO    BABCOCK    &  WILCOX    CHAIN  GRATE  STOKERS  IN  COURSE  OF  ERECTION 

WITH   A    1220   HORSE-POWER   BABCOCK   &  WILCOX   BOILER  AT  THE  FISK 

ST.  STATION   OF  THE  COMMONWEALTH  EDISON   CO.,  CHICAGO,  ILL. 


ADVANTAGES  OF   CHAIN   GRATE 

STOKERS 

ATOMATIC  stokers  may  be  divided  into  three  general  classes — the 
underfeed,  the  overfeed,  and  the  traveling  grate.  In  efficiency  of 
combustion,  other  conditions  being  equal,  there  will  be  no  appreciable 
difference  with  the  different  types  of  stoker,  provided  that  the  proper  type  is 
selected  for  the  grade  of  fuel  used  and  the  conditions  of  operations  to  be  fulfilled. 
No  stoker  will  satisfactorily  handle  all  classes  of  fuel,  and  in  making  a  selection 
care  must  be  taken  to  suit  the  type  to  the  fuel  and  the  operating  conditions  of 
the  service  to  be  performed. 

That  the  chain  grate  stoker  more  fully  meets  the  requirements  of  automatic 
firing  than  do  other  types  is  exemplified  by  the  fact  that  there  are  more  manu- 
facturers turning  out  this  class  of  apparatus  than  any  other  class  of  stoker. 
Further,  in  European  practice,  particularly  in  Great  Britain  and  Germany  where 
the  highest  possible  efficiencies  are  sought,  the  chain  grate  stoker  is  used  to  the 
almost  entire  exclusion  of  other  types  of  stoker. 

In  this  country  the  field  of  usefulness  of  the  chain  grate  stoker  has  been,  up 
to  the  present  time,  largely  confined  to  the  burning  of  the  more  highly  volatile 
coals  of  the  Middle  West.  With  such  coals,  chain  grates  have  given  the  most 
satisfactory  service — efficiencies  and  capacities  being  secured  that  are  among  the 
highest  on  record — and  this,  oftentimes,  with  coals  that  could  not  be  handled 
satisfactorily  on  other  types  of  stoker. 

More  recently,  attention  has  been  given  to  the  adaptation  of  this  type  of 
stoker  to  the  burning  of  the  less  volatile  coals  with  results  which  are  eminently 
satisfactory  and  full  of  promise  for  the  future  of  the  stoker  with  this  class  of  fuel. 

Chain  grate  stokers  are  not  new,  having  been  one  of  the  first  types  of 
apparatus  offered  for  automatically  feeding  coal  to  a  boiler  furnace.  In  the 
general  design  and  operation  of  the  chain  grate  stoker,  there  are  a  number  of 
features  that  give  it  a  distinct  advantage  over  other  types.  In  operation  the  fuel 
is  fed  uniformly  to  the  forward  end  of  the  grate,  the  volatile  gases  are  distilled 
on  this  portion,  and  passing  over  the  incandescent  fuel  bed  are  fully  consumed. 
The  progress  of  the  fuel  from  the  green  coal  at  the  front  of  the  furnace  to 
incandescent  coke  and  finally  to  ash  at  the  rear  of  the  grate  is  uniform  and 
continuous.  This  progressive  combustion  prevents  the  sudden  liberation  of  a 
large  volume  of  gas  such  as  would  occur  where  a  shovelful  of  green  coal  is  fired 
by  hand  upon  the  top  of  an  incandescent  bed  of  fuel. 

The  grate  is  in  the  form  of  a  chain,  of  which  approximately  only  one-third 
is  under  the  fire  at  one  time.  With  most  coals,  and  assuming  that  proper  draft 
conditions  obtain,  or  that  there  is  a  suction  available  in  the  boiler  furnace  under 
all  conditions,  the  small  portion  of  the  grate  under  the  fire  and  the  continual 
change  of  such  portion  gives  ample  provision  for  cooling.  The  grate,  formed  as 

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it  is  of  relatively  short  links,  presents  a  flat  surface  to  the  fire  and  permits  none 
of  the  links  to  extend  into  the  fire.  These  features  lead  to  a  long  life  of  the 
grate  and  the  renewal  of  the  grate  bars  or  links  becomes  a  negligible  factor 
instead  of  a  controlling  feature,  as  is  the  case  in  some  other  forms  of  stoker. 
The  long  life  of  a  chain  grate  is  perhaps  best  exemplified  by  the  fact  that  there 
are  stokers  of  this  description  which  have  been  in  operation  for  over  fifteen  years 
on  the  links  of  which  the  casting  marks  are  still  plainly  visible. 

With  the  chain  grate,  the  automatic  phase  of  feeding  is  carried  to  a  higher 
point  than  is  possible  with  most  other  types  of  stoker.  Not  only  is  the  feed 
continuous,  as  is  the  case  in  practically  all  stokers,  but  the  cleaning  of  the  fires 
is  continuous.  Reference  has  already  been  made  to  the  almost  entire  absence 
of  the  necessity  of  working  the  fires  but  practically  all  types  of  stokers,  except 
chain  grates,  require  some  definite  cleaning  period,  resulting  usually  from  the 
necessity  of  dumping  auxiliary  flat  or  coking  grates.  At  such  times  the  furnace 
conditions  approach  closely  those  of  the  cleaning  periods  in  hand-fired  practice, 
with  the  consequent  losses  in  efficiency  and  periodic  intervals  of  smoking.  Chain 
grate  stokers  on  the  other  hand  are  being  cleaned  continuously  by  the  passage  of 
the  ash  over  the  rear  of  the  grates  and  the  furnace  conditions  are  not  varied  by 
having  to  dump  the  ash  and  shake  down  the  fires  at  the  cleaning  intervals. 
While  such  cleaning  periods  with  other  stokers  may  be  far  apart,  still  their 
necessity  causes  a  lowering  of  the  average  of  furnace  efficiency  in  a  long  run. 
The  automatic  cleaning  of  a  chain  grate  fire,  on  the  other  hand,  enables  test 
conditions  in  the  furnace  to  be  maintained  over  any  period  of  time  required. 

The  maintenance  cost  of  chain  grate  stokers  is,  in  most  instances,  con- 
siderably less  than  that  of  other  types.  The  grates  are  the  only  portion  exposed 
to  the  fire,  and  it  has  been  pointed  out  that  with  most  coals  and  proper  draft 
conditions  ample  provision  is  made  for  their  cooling.  As  it  is  practically 
impossible  with  adequate  draft  to  burn  out  any  part  of  the  stoker,  the  mainten- 
ance cost  of  this  type  of  apparatus  is  reduced  to  a  minimum.  Chain  grate 
stokers  from  the  nature  of  their  operation  are  comparatively  easy  on  the  furnace 
brickwork,  and  here,  again,  the  maintenance  expense  is  low  as  compared  with 
that  where  other  types  of  stokers  are  used. 

From  the  continuous  cleaning  it  is  clear  that  with  proper  operation  the 
furnace  will  be  practically  smokeless  at  all  times. 

A  distinct  advantage  of  this  class  of  stoker  is  the  fact  that  the  entire  stoker 
may  be  readily  removed  from  the  furnace  for  inspection  or  repair  without  in  any 
way  disturbing  the  setting  or  the  boiler,  while  with  other  types,  for  such  removal, 
the  stoker  must  be  dismantled. 


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16 


THE    BABCOCK    &  WILCOX    CHAIN 
GRATE    STOKER 

THE  advantages  of  the  chain  grate  stoker  as  a  class  have  been  pointed 
out.  The  success  of  an  individual  stoker  of  this  class,  however,  is  dependent 
upon  the  care  exercised  in  the  details  of  its  design  and  construction  to 
obviate  difficulties  to  which  improper  attention  to  such  features  would  lead. 

The  care  necessary  in  such  details  to  secure  the  successful  operation  of  this 
class  of  stoker  is,  apart  from  the  description  of  the  apparatus  as  a  whole,  perhaps 
best  illustrated  by  certain  specific  features  embodied  in  the  Babcock  &  Wilcox 
chain  grate  stoker. 

A  bridge  wall  water  box  is  supplied  as  a  regular  part  of  the  stoker  equipment. 

Where  a  proper  bridge  wall  water  box  is  not  supplied  as  a  part  of  the  stoker, 
trouble  is  bound  to  arise  from  the  leakage  of  air  at  the  rear  of  the  furnace.  The 
brickwork  of  the  bridge  wall  becomes  eroded,  leaving  large  irregular  holes  for 
the  admission  of  air.  Combustion  has  been  completed  by  the  time  the  fire  has 
reached  this  point  and  any  further  admission  of  air  simply  dilutes  the  products  of 
combustion  and  increases  the  loss  in  the  stack  gases. 

Further,  a  bridge  wall  water  box  acts  as  a  protection  to  the  links  of  the  grate. 
These  links  in  starting  to  turn  over  the  rear  sprocket,  break  from  the  flat  surface 
of  the  grate  and  their  corners  extend  upward.  With  the  bridge  wall  water  box  so 
placed  that  such  an  action  of  the  links  takes  place  after  they  have  passed  its  face, 
there  is  no  danger  of  burning  these  projecting  corners. 

Efficient  side  seals  are  provided. 

Without  proper  side  seals  a  large  leakage  of  air  will  occur  at  the  sides  of  the 
furnace  with  a  resulting  effect  on  the  efficiency  of  the  boiler  as  bad  as  through 
leakage  at  the  rear  of  the  grate.  In  either  case,  such  leakage  chokes  all  gas 
passages,  flue  and  stack,  decreases  the  draft  and  lowers  the  amount  of  air  drawn 
through  the  fuel  bed,  with  the  consequent  reduction  of  capacity  and  economy  of 
the  boiler. 

The  construction  of  the  stoker  as  a  whole  is  of  such  a  rugged  nature  as  to 
allow  continuous  operation  without  shutting  down  for  repairs,  over  long  periods  of 
time.  Such  a  feature  is  obviously  a  necessity  if  the  stoker  is  to  be  considered  a 
commercial  success. 

The  following  detailed  description  of  the  Babcock  &  Wilcox  chain  grate 
stoker,  together  with  a  study  of  the  accompanying  illustrations,  will  indicate  the 
reasons  for  the  particular  success  with  which  it  has  met  the  requirements  of  a 
good  stoker  as  above  outlined. 

The  grate  proper  is  made  up  of  common  and  driving  links,  the  latter  being 
2/6  inch  wider  than  the  former  at  the  hub,  both  links  being  4  inches  deep.  The 
links  of  any  row  are  held  together  by  a  steel  rod  passing  through  their  hubs. 
These  links  are  machine  molded  with  greatest  accuracy  from  metal  patterns,  and 

17 


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18 


no  variation  in  excess  of  ^  inch  is  tolerated.  The  faces  of  the  links  are  TV  inch 
narrower  than  the  hubs,  thus  giving  a  space  of  1A  inch  between  adjacent  links 
sidewise  for  the  admission  of  air.  Half-round  grooves  are  cast  in  the  sides  of  the 
links  for  increasing  the  air  space,  these  grooves  being  so  arranged  that  they 
cannot  come  opposite  to  each  other  in  adjacent  links. 

The  chain  passes  over  sprocket  wheels  of  large  diameter  at  the  front  and 
rear  of  the  grate,  these  being  keyed  to  a  steel  shaft  of  ample  diameter.  The 
shafts  run  in  solid  cast-iron  machined  bearings  of  generous  proportions  which  are 
mounted  in  rectangular  guides  at  the  rear  of  the  cast-iron  side  frames,  and  in 
the  cast-iron  sections  or  cheek  pieces  which  are  bolted  to  these  frames  at  the  front. 
Adjustment  is  provided  by  means  of  large  diameter  screws  for  both  front  and 
rear  bearings.  Such  adjustment  makes  possible  the  taking  up  of  any  sag  in 
the  chain  or  allows  removal  of  any  link  without  dissembling  the  whole  stoker. 
Compression  grease  cups  for  lubrication  of  these  bearings  are  located  at  the  stoker 
front  and  are  piped  to  front  and  rear  bearings. 

The  upper  part  of  the  chain  is  supported  on  rollers  spaced  9  inches  apart, 
and  the  lower  portion  on  rollers  spaced  1 8  inches  apart.  These  rollers  are  of 
wrought-iron  pipe,  to  the  ends  of  which  cast-iron  bushings  are  fitted.  The 
bushings  run  on  stationary  wrought-steel  axles  extending  from  side  to  side  of 
the  grate  and  supported  by  the  cast-iron  frames. 

SIDE  FRAMES  —  The  side  frames  are  of  heavy  cast-iron  construction  with 
diagonal  web  members,  which  make  them  unusually  strong  as  beams,  and  at  the 
same  time  afford  ample  access  to  the  space  between  the  upper  and  lower  chain. 
These  frames  are  3}^  inches  wide  at  the  top  and  present  an  upper  surface 
flush  with  the  top  of  the  grate.  The  inner  sides  of  the  flush  portions 
are  machined  and  form  a  guide  against  which  the  side  links  of  the  chain 
rub.  At  the  outer  edges  of  the  side  frames,  side  seals  are  held  by  guide  bolts 
which  allow  them  a  vertical  motion.  These  seals  are  held  by  weighted  levers 
against  the  under  surface  of  cast-iron  side  plates  which  are  built  into  the  brick- 
work and  overhang  the  side  frames  of  the  stoker. 

The  vertical  motion  of  these  seals  allows  the  complete  exclusion  of  air  at 
the  sides  of  the  furnace  and  the  fire  in  this  way  is  kept  from  burning  out  at  the 
sides.  This  motion  also  permits  the  side  seals  to  be  depressed  when,  for  any 
reason,  it  is  necessary  to  withdraw  the  stoker. 

To  the  front  of  the  frame  proper  cast-iron  cheek  pieces  are  bolted,  these 
forming  the  extension  which  projects  beyond  the  furnace  front  line. 

The  side  frames  and  cheek  pieces  are  maintained  at  a  proper  distance  from 
each  other  by  means  of  steel  spacing  bolts  front  and  rear,  a  cast-iron  cross  beam 
at  the  front,  which  also  maintains  the  cheek  pieces  in  a  vertical  position,  a  wrought- 
steel  channel  at  the  front  of  the  cheek,  a  second  wrought-steel  channel  between  the 
chains  at  the  front,  and  a  third  wrought-steel  channel  between  the  chains  at  the  rear. 

This  last  wrought-steel  channel  forms  a  part  of  the  baffle  at  the  rear  of 
the  stoker  for  excluding  the  air  from  this  space.  Below  the  channel  a  steel  plate 

19 


BABCOCK   &  WILCOX    CHAIN   GRATE   STOKER   INSTALLED  WITH  A  WROUGHT- 

STEEL   VERTICAL     HEADER    BOILER,  EQUIPPED    WITH    A 

BABCOCK   &  WILCOX    SUPERHEATER 


baffle  stiffened  by  angles  forms  an  additional  spacing  piece.  Hinged  to  the 
bottom  of  this  stationary  baffle  plate  a  swinging  steel  plate,  stiffened  by  angles, 
extends  to  the  bottom  of  the  ashpit  between  the  stoker  rails  completing  the  seal 
at  the  rear.  A  chain  connected  to  this  hinged  baffle  is  brought  to  the  front  of 
the  stoker  where  it  may  be  fastened.  By  this  means  the  baffle  may  be  held  in 
any  position  and  a  greater  or  less  amount  of  air  admitted  at  the  rear  to  meet  the 
varying  conditions  of  combustion.  When  this  large  damper  is  raised  it  affords 
easy  access  to  the  rear  of  the  stoker  without  withdrawing  it  from  the  furnace. 

Diagonal  rods  from  side  to  side  maintain  the  frames  at  right  angles  to  the 
cross  ties  and  shafts. 

TRACK  WHEELS — The  track  wheels  are  of  heavy  cast  iron,  18  inches  in  diame- 
ter, running  on  steel  axles.  These  axles  are  tight  in  the  wheels  and  revolve  in 
machined  bearings  at  either  side  of  the  wheel,  the  bearings  being  integral  with 
the  frames  and  front  cheeks  of  the  stoker. 

RAILS — Stoker  rails  are  furnished  as  a  part  of  the  standard  stoker  equip- 
ment. These  are  heavy  angles  to  which  guide  strips  are  riveted  and  are  of 
sufficient  length  to  enable  the  stoker  to  be  entirely  drawn  from  the  furnace. 

COAL  HOPPER — A  coal  hopper  of  large  capacity  is  formed  at  the  front  by 
the  cast-iron  side  cheeks  of  the  stoker  and  by  an  inclined  steel  sheet  stiffened 
by  angles.  The  lower  edge  of  this  plate  is  supported  by  lugs  cast  on  the  inner 
faces  of  the  stoker  cheeks,  and  the  upper  edge  is  supported  by  removable  pins 
through  these  side  cheeks.  The  pins  are  attached  to  the  side  cheeks  by  chains 
and  have  large  enclosed  handles  by  which  they  can  be  readily  withdrawn.  The 
whole  is  so  arranged  that  by  the  withdrawal  of  these  pins  the  plate  may  be 
allowed  to  drop  and  any  coal  in  the  stoker  hopper  and  the  fire  itself  may 
be  quickly  drawn  out  onto  the  boiler  room  floor,  if  for  any  reason  such  action 
is  necessary. 

STOKER  COAL  GATE  —  A  coal  gate,  sliding  vertically  in  removable  guides 
bolted  to  the  inner  surface  of  the  cast-iron  cheek  pieces,  furnishes  a  method  of 
regulating  the  thickness  of  the  fuel  bed  as  fed  to  the  forward  end  of  the  grate. 
The  height  of  this  gate  is  regulated  by  a  hand  wheel  through  a  worm  wheel  and 
cross  shaft,  which  raises  or  lowers  the  chains  from  which  the  gate  is  hung.  The 
inner  surface  of  this  gate  is  lined  with  fire  brick  which  may  be  removed  as 
occasion  demands  without  interfering  with  the  operation  of  the  stoker. 

STOKER  DRIVE — The  front  sprocket  shaft  is  driven  by  a  heavy  cast-iron 
worm  wheel.  This  worm  wheel  engages  a  cast-iron  worm  secured  by  fitted 
taper  keys  to  a  worm  shaft,  the  outer  end  of  which  is  squared,  and  to  the  inner 
end  of  which  is  keyed  one  of  a  pair  of  mitre  gears.  Another  mitre  gear  which 
engages  this  is  actuated  by  a  ratchet  wheel.  Long  and  short  tool  steel  pawls 
drive  this  ratchet  wheel  from  a  cast-iron  ratchet  arm.  A  second  pair  of  tool 
steel  pawls  prevents  the  ratchet  wheel  from  moving  backward.  The  pawls 
referred  to  in  each  case  differ  in  length  by  an  amount  equal  to  one-half  of  a  tooth 
of  the  ratchet  wheel,  with  the  result  that  a  fineness  of  feed  is  possible  equivalent 


DRIVING    MECHANISM   OF  BABCOCK   &  WILCOX    CHAIN  GRATE 
STOKER    WITH    CASING    REMOVED 


to  that  of  a  ratchet  wheel  with  twice  the  number  of  teeth  of  that  supplied, 
without  the  disadvantage  of  fine  teeth  on  this  wheel. 

The  bearings  for  the  driving  mechanism  are  supported  by  cast-iron  frames 
bolted  to  one  cheek  piece. 

The  driving  mechanism  as  a  whole  is  completely  encased  with  a  cast-iron 
housing  which  gives  effectual  protection  to  these  parts  and  by  preventing  the 
accumulation  of  coal  dust  on  such  parts  assures  the  absence  of  wear  from 
this  cause. 

The  ratchet  arm  referred  to  is  driven  from  an  eccentric  rod,  the  radius  of 
whose  attachment  to  the  ratchet  arm 
may  be  changed  at  will  to  increase  or 
decrease  the  amount  of  feed  for  each 
revolution  of  the  eccentric.  A  spring- 
safety  stop  in  the  eccentric  rod  limits  the 
power  which  may  be  transmitted  from 
the  eccentric,  to  prevent  breakage  in 
case  any  foreign  object  blocks  the  motion 
of  the  stoker. 

By  simply  lifting  the  pawls  out  of 
engagement  with  the  ratchet  wheel  and 
applying  a  crank  to  the  squared  end  of 
the  worm  shaft,  the  grate  may  be  run  in 
or  out  by  hand.  It  is  one  of  the  require- 
ments in  the  erection  of  the  stoker  that 
one  man  be  able  to  operate  the  grate  in 
either  direction  with  this  crank  before 
any  power  is  applied. 

STOKER  WATER  Box  —  A  stoker 
water  box  is  a  part  of  the  standard 
stoker  equipment.  At  the  bridge  wall, 
such  a  bridge  wall  water  box  of  forged 
steel,  7^  inches  square  outside,  is 
carried  transversely  across  the  end  of 
the  stoker.  The  water  box  acts  as  an 
air  seal  at  this  point,  limits  the  thickness 
of  the  bed  of  consumed  fuel  which  may 

pass  under  it,  prevents  the  admission  of  large  quantities  of  air  around  the  end 
of  the  grate,  and  by  acting  as  a  means  of  solidifying  the  rear  of  the  fire,  prevents 
an  uneven  admission  of  air  through  this  portion  of  the  fuel  bed. 

This  water  box  is  connected  into  the  circulation  of  the  boiler,  requiring  no 
other  provision  for  keeping  it  cool.  The  exit  connection  from  the  box  is  made 
in  a  position  which  will  completely  drain  the  box  of  any  steam  which  may  form 
within  it,  and  the  possibility  of  overheating  is  avoided  by  the  positive  circulation 


STOKER   DRIVE    WITH    CASING 
REMOVED— FRONT  VIEW 


BABCOCK   &   WILCOX    CHAIN    GRATE    STOKER   INSTALLED  WITH    A    STIRLING 
BOILER,   EQUIPPED   WITH    A    BABCOCK   &  WILCOX    SUPERHEATER 


24 


maintained.  The  exposed  surface  of  the  box  is  active  in  the  absorption  of  heat 
and  the  losses  entailed  by  a  separate  circulation  for  cooling  are  avoided. 

The  connections  to  and  from  the  stoker  water  box  are  made  by  boiler  tubes 
expanded  into  counterbored  seats.  Provision  is  made  for  internal  inspection  of 
the  box  by  supplying  handholes  through  which  the  joints  may  be  re-expanded  if 
such  a  course  should  for  any  reason  be  necessary. 

LUBRICATION — Ample  provision  is  made  for  lubricating  all  bearings.  The 
drive  housing,  which  has  been  described,  is  partially  filled  with  oil,  thus  keeping 
the  teeth  of  the  driving  wheel  slushed  at  all  times. 

WORKMANSHIP  AND  MATERIAL  —  Materials  entering  into  the  construction 
of  the  stoker  are  of  the  best  procurable  for  the  duty  to  be  performed,  and  the 
workmanship  in  its  building  is  of  the  highest  class. 

Bearings  which  are  subject  to  slow  motion  and  heavy  pressure  are  between 
machine  steel  and  machined  cast-iron  surfaces,  which  experience  has  shown  to 
give  the  best  service.  Bearings  on  the  worm  shaft  are  babbited.  Bronze  thrust 
collars  are  provided  for  receiving  the  thrust  of  the  worm.  Bearings  for  the  coal 
gate  operating  device  are  machined.  All  machining  is  done  with  jigs  and 
templates  so  that  repair  parts  are  interchangeable. 


BABCOCK    &    WILCOX    CHAIN    GRATE    STOKER    INSTALLED  WITH    A    RUST 
BOILER,   EQUIPPED    WITH    A    BABCOCK    &  WILCOX    SUPERHEATER 

26 


THE    BABCOCK    &   WILCOX    CHAIN 
GRATE   STOKER    IN    SERVICE 

THE  Babcock  &  Wilcox  chain  grate  stoker  was  first  commercially  manu- 
factured in    1893.     Its  performance  since  that  time  with  the  coals,  for 
which  experience  has  shown  it  is  particularly  adapted,  has  given  eminent 
satisfaction  in  plants  operating  under  widely  varying  conditions  of  load.     This  is 
perhaps  best  exemplified  by  the  large  number  of  repeat  orders  received  for  the 
apparatus. 

Continuous  operation  has  shown  that  the  upkeep  cost  of  the  stoker  iron 
work  is  remarkably  low  and,  where  properly  operated,  is  practically  negligible. 
As  an  example,  it  may  be  cited  that  in  certain  power  stations,  where  the  service 
is  the  most  severe  that  can  be  found  in  boiler  operating  practice,  there  are 
stokers  that  have  been  operated  continuously  for  over  fifteen  years,  on  the  links 
of  which  the  original  casting  marks  are  still  plainly  visible,  and  the  upkeep  cost  of 
the  iron  work  of  these  stokers  has  been  considerably  less  than  $50.00  per  stoker, 
or  less  than  $3.00  per  stoker  per  year.  The  long  life  and  low  maintenance  cost  are 
due,  as  has  been  indicated,  to  the  inherent  advantages  of  the  chain  grate  stoker 
as  a  class,  and  particularly  the  rugged  construction  of  the  Babcock  &  Wilcox 
stoker  as  representative  of  the  type. 

The  appended  table  of  tests*  indicates  the  efficiences  and  capacities  that  may 
be  obtained  from  different  boilers  when  set  with  Babcock  &  Wilcox  chain  grate 
stokers.  In  considering  the  figures  presented  in  this  table  it  is  to  be  remem- 
bered that  while  they  represent  test  conditions,  such  conditions  may  be  more 
closely  approached  in  operating  practice  with  the  chain  grate  stoker  than  with 
any  other  type  of  stoker,  and  that  because  of  the  continuous  and  efficient  cleaning 
of  the  fires,  such  results  may  be  obtained  over  indefinite  periods  of  time  and  are 
not  limited  to  tests  of  but  a  few  hours'  duration. 


*See  pages  41  to  47. 

27 


EDWARD    FORD     PLATE    GLASS    CO.,    ROSSFORD,    OHIO.     BABCOCK   &  WILCOX 

CHAIN    GRATE    STOKERS    INSTALLED  WITH   4000   HORSE    POWER 

OF    STIRLING    BOILERS 


STOKER-FIRED    FURNACE 
BRICKWORK 

THE  consideration  of  brickwork  for  stoker-fired  furnaces  may  be  divided  into 
three  parts,  namely :  furnace  design,  quality  of  brick  used,  and  workman- 
ship in  the  laying  up  of  brick.  The  question  as  here  considered  is 
limited  to  the  furnace  proper,  and  deals,  therefore,  only  with  fire  brick. 

DESIGN  —  The  design  of  the  furnace  is  obviously  of  the  greatest  importance. 
Such  design,  however,  varies  so  widely  with  different  types  of  boilers  and  stokers, 
different  fuels,  and  different  operating  conditions  that  no  general  statement  that 
.will  apply  to  all  cases  may  be  made  as  to  what  constitutes  a  proper  furnace 
design.  The  number  of  combinations  possible  of  boilers,  stokers,  fuels  and 
operating  conditions  is  so  very  extensive  that  no  attempt  will  be  made  here  to 
suggest  a  furnace  design.  Each  individual  installation  of  boiler  and  stoker 
should  be  considered  by  itself  and  the  furnace  design  based  upon  experience  as 
to  what  has  given  the  most  satisfactory  service  for  a  similar  set  of  conditions. 

QUALITY  OF  FIRE  BRICK — The  modern  tendency  toward  high  overloads  has 
increased  greatly  the  severity  of  t^he  service  under  which  furnace  brickwork 
is  called  upon  to  stand,  and  to  a  very  great  extent  the  life  of  the  furnace  is 
dependent  upon  the  quality  of  fire  brick  entering  into  its  construction. 

Until  very  recently,  the  important  characteristic  upon  which  to  base  a 
judgment  of  the  suitability  of  fire  brick  for  use  in  connection  with  boiler  settings 
has  been  considered  the  melting  point,  or  the  temperature  at  which  the  brick 
will  liquify  and  run.  Experience  has  shown,  however,  that  this  point  is  only 
important  within  certain  limits  and  that  the  real  basis  upon  which  to  judge 
material  of  this  description  is,  from  the  boiler  man's  standpoint,  the  quality  of 
plasticity*  under  a  given  load.  This  tendency  of  a  brick  to  become  plastic 
occurs  at  a  temperature  much  below  the  melting  point  and  to  a  degree  that  may 
cause  the  brick  to  become  deformed  under  the  stress  to  which  it  is  subjected. 
The  allowable  plastic  or  softening  temperature  will  naturally  be  relative  and 
dependent  upon  the  stress  to  be  endured. 

With  the  plasticity  the  determining  factor,  the  perfect  fire  brick  is  one  whose 
critical  point  of  plasticity  lies  well  above  the  working  temperature  of  the  fire.  It 
is  probable  that  there  are  but  few  brick  on  the  market  which  would  not  show,  if 
tested,  this  critical  temperature,  at  the  stress  met  with  in  arch  construction,  at  a 


*  A  method  of  testing  brick  for  this  characteristic  is  given  in  the  Technologic  Paper  No.  7  of  the  Bureau  of 
Standards  dealing  with  "  The  Testing  of  Clay  Refractories,  with  Special  Reference  to  Their  Load  Carrying 
Capacity  at  Furnace  Temperatures."  Referring  to  the  test  for  this  specific  characteristic,  this  publication 
recommends  the  following :  "  When  subjected  to  the  load  test  in  a  manner  substantially  as  described  in  this 
bulletin,  at  1350  degrees  centigrade  (2462  degrees  Fahrenheit),  and  under  a  load  of  50  pounds  per  square  inch,  a 
standard  fire  brick  tested  on  end  should  show  no  serious  deformation  and  should  not  be  compressed  more  than  one 
inch,  referred  to  the  standard  length  of  nine  inches." 

In  the  Bureau  of  Standards  Test  for  softening  temperature,  or  critical  temperature  of  plasticity  under  the 
specified  load,  the  brick  are  tested  on  end.  In  testing  fire  brick  for  boiler  purposes  a  better  method  is  that  of 
testing  the  brick  as  a  beam  subjected  to  its  own  weight  and  not  on  end.  This  method  has  been  used  for  years  in 
Germany  and  is  recommended  by  the  highest  authorities  in  ceramics.  It  takes  into  account  the  failure  of  tension 
in  the  brick  as  well  as  by  compression  and  thus  covers  the  tension  element  which  is  important  in  arch  construction. 

29 


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CJ   fc, 

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o 

„  •    PH 

S  w 

si 


30 


point  less  than  2400  degrees.  The  fact  that  an  arch  will  stand  for  a  long  period 
under  furnace  temperatures  considerably  above  this  point  is  due  entirely  to  the 
fact  that  its  temperature  as  a  whole  is  far  below  the  furnace  temperature  and 
only  about  10  per  cent  of  its  cross  section  nearest  the  fire  approaches  the  furnace 
temperature.  This  is  borne  out  by  the  fact  that  arches  which  are  heated  on  both 
sides  to  the  full  temperature  of  the  ordinary  furnace  will  first  bow  down  in  the 
middle  and  eventually  fall. 

The  plastic  point  under  a  unit  stress  of  100  pounds  per  square  inch,  which 
may  be  taken  as  the  maximum  arch  stress,  should  be  above  2800  degrees  to  give 
perfect  results  and  should  be  above  2400  degrees  to  enable  the  brick  to  be  used 
with  any  degree  of  satisfaction. 

The  other  characteristics  by  which  the  quality  of  a  fire  brick  is  to  be  judged  are : 

FUSION  POINT  —  In  view  of  the  fact  that  the  critical  temperature  of  plasticity 
is  below  the  fusion  point,  this  is  only  important  as  an  indication  from  high  fusion 
point  of  a  high  temperature  of  plasticity. 

HARDNESS  —  This  is  a  relative  quality  based  on  an  arbitrary  scale  of  10  and 
is  an  indication  of  probable  cracking  and  spalling.  Provided  hardness  is  sufficient 
to  enable  the  brick  to  withstand  its  load,  additional  hardness  is  a  detriment  rather 
than  an  advantage. 

EXPANSION — The  lineal  expansion  per  brick  in  inches.  This  characteristic 
in  conjunction  with  hardness  is  a  measure  of  the  physical  movement  of  the  brick  as 
affecting  a  mass  of  brickwork,  such  movement  resulting  in  cracked  walls,  etc.  The 
expansion  will  vary  between  wide  limits  in  different  brick  and  provided  such  expan- 
sion is  not  in  excess  of,  say,  .05  inch  in  a  9-inch  brick,  when  measured  at  2600 
degrees,  it  is  not  particularly  important  in  a  properly  designed  furnace,  though 
in  general  the  smaller  the  expansion  the  better. 

COMPRESSION  — The  strength  necessary  to  cause  crushing  on  the  brick  at 
the  center  of  the  4  ^  -inch  face  by  a  steel  block  one  inch  square.  The  compression 
should  ordinarily  be  low,  a  suggested  standard  being  that  a  brick  show  signs  of 
crushing  at  7500  pounds. 

SIZE  OF  NODULES — The  average  size  of  flint  grains  when  the  brick  is  care- 
fully crushed.  The  scale  of  these  sizes  may  be  taken:  Small,  size  of  anthracite 
rice ;  large,  size  of  anthracite  pea. 

RATIO  OF  NODULES — The  percentage  of  a  given  volume  occupied  by  the 
flint  grains.  This  scale  may  be  considered  :  High,  90  to  100  per  cent ;  medium, 
50  to  90  per  cent ;  low,  10  to  50  per  cent. 

The  statement  of  characteristics  suggested  as  desirable,  are  for  arch  purposes 
where  the  hardest  service  is  met.  For  side  wall  purposes  the  compression  and 
hardness  limit  may  be  raised  considerably  and  the  plastic  point  lowered. 

From  the  nature  of  fire  brick  their  value  can  only  be  considered  from  a 
relative  standpoint.  Generally  speaking,  what  are  known  as  first-grade  fire  brick 
may  be  divided  into  three  classes,  though  only  the  first  two  are  ordinarily  considered 
suitable  for  stoker  work.  Table  I  gives  the  characteristics  of  these  two  classes, 

31 


WASHINGTON  TERMINAL  CO.,  WASHINGTON,  D.  C.    BABCOCK   &  WILCOX  CHAIN 

GRATE    STOKERS    INSTALLED  WITH   3000   HORSE    POWER   OF  CROSS  DRUM 

BABCOCK    &    WILCOX    BOILERS 

32 


Class  A  being  for  stoker-fired  furnaces  where  high  overloads  are  to  be  expected 
or  other  extreme  conditions  of  service  are  apt  to  occur,  and  Class  B  being  for 
stoker  settings  where  it  is  known  that  no  excessive  overloads  will  be  required. 


TABLE  1 


Characteristics 

Class  A 

Class  B 

Fuse  point,  degrees  Fahrenheit  .     .     . 
Compression,  pounds     

Safe  at  3200-3300  deg.  F. 

6  SOO—  7  SOO 

Safe  at  2900-3200  deg.  F. 
7500  1  1  ooo 

Hardness,  relative      

1—2 

2    A 

Size  of  nodules      

Medium 

Medium  to  medium  large 

Ratio  of  nodules   ... 

High 

Medium  to  high 

An  approximate  determination  of  the  quality  of  a  fire  brick  may  be  made 
from  the  appearance  of  a  fracture.  Where  such  a  fracture  is  open,  clean,  white 
and  flinty,  the  brick  in  all  probability  is  of  a  good  quality.  If  this  fracture  has 
the  fine  uniform  texture  of  bread,  the  brick  is  probably  poor. 

In  considering  the  heavy  duty  of  brick  in  boiler  furnaces,  experience  shows 
that  arches  are  ordinarily  the  cause  of  trouble.  These  may  fail  from  the 
following  causes : 

Bad  workmanship  in  laying  up  of  the  brick.     This  feature  is  treated  later. 

The  tendency  of  brick  to  become  plastic  at  a  temperature  below  the  fusing 
point.  The  limits  of  allowable  temperature  have  been  shown. 

SPALLING — This  action  occurs  on  the  inner  ends  of  combustion  arches 
where  they  are  swept  by  gases  at  a  high  velocity  at  the  full  furnace  temperature. 
The  most  troublesome  spalling  arises  from  cold  air  striking  the  heated  brickwork. 
Inasmuch  as  rapid  temperature  changes  are  to  a  great  degree  eliminated 
in  stoker-fired  work,  this  cause  of  failure  is  less  frequent  than  formerly. 
Furthermore,  there  are  a  number  of  brick  on  the  market  practically  free  from 
such  defects  and  where  a  new  brick  is  considered  it  can  be  tried  out  and 
discarded  if  the  defect  is  found  to  exist. 

FAILURE  FROM  THE  EXPANSIVE  POWER  OF  BRICK  is  also  rare,  due  to  the 
fact  that  there  are  a  number  of  brick  in  which  the  expansion  is  well  within 
the  allowable  limits  and  the  ease  with  which  such  defects  may  be  determined 
before  a  brick  is  used. 

FAILURE  THROUGH  CHEMICAL  DISINTEGRATION  —  Failure  through  this 
cause  is  found  only  occasionally  in  brick  containing  a  high  percentage  of 
iron  oxide. 

With  the  grade  of  brick  selected  best  suited  to  the  service  of  the  boiler  to 
be  set,  the  other  factor  affecting  the  life  of  the  setting  is  the  laying.  It  is 
probable  that  more  setting  difficulties  arise  from  the  improper  workmanship  in 
the  laying  up  of  brick  than  from  poor  material,  and  to  insure  a  setting  which 
will  have  even  a  reasonable  life  it  is  necessary  that  the  masonry  work  be  done 

33 


en 


34 


most  carefully.     This  is   particularly  true  where  the  boiler   is   of  a  type  which 
requires  combustion  arches  in  the  furnace. 

All  fire  brick  should  be  dry  when  used  and  protected  from  moisture  until 
used.  Each  brick  should  be  dipped  in  a  thin  fire-clay  wash,  "rubbed  and 
shoved"  into  place,  and  tapped  with  a  wooden  mallet  until  it  touches  the  brick 
next  below  it.  It  must  be  recognized  that  fire  clay  is  not  a  cement  and  that  it 
has  little  or  no  holding  power.  Its  action  is  that  of  a  filler  rather  than  a  binder 
and  no  fire-clay  wash  should  be  used  which  has  a  consistency  sufficient  to  permit 
the  use  of  a  trowel. 

All  fire-brick  linings  should  be  laid  up  four  courses  of  headers  and  one 
stretcher.  Furnace  center  walls  should  be  entirely  of  fire  brick.  If  the  center 
of  such  walls  is  built  of  red  brick,  they  will  often  melt  down  and  cause  the 
failure  of  the  wall  as  a  whole. 

Fire-brick  arches  should  be  constructed  of  selected  brick  which  are  smooth, 
straight  and  uniform.  The  forms  on  which  such  arches  are  built,  called  arch 
centers,  should  be  constructed  of  batten  strips  not  over  2  inches  wide.  The 
brick  should  be  laid  on  these  centers  in  courses,  not  in  rings,  each  joint  being 
broken  with  a  bond  equal  to  the  length  of  half  a  brick.  Each  course  should  be 
first  tried  in  place  dry,  and  checked  with  a  straight  edge  to  insure  a  uniform 
thickness  of  joint  between  courses.  Each  brick  should  be  dipped  on  one  side 
and  two  edges  only  and  tapped  into  place  with  a  mallet.  Wedge  brick  courses 
should  be  used  only  where  necessary  to  keep  the  bottom  faces  of  the  straight 
brick  course  in  even  contact  with  the  centers.  When  such  contact  cannot  be 
exactly  secured  by  the  use  of  wedge  brick,  the  straight  brick  should  lean  away 
from  the  center  of  the  arch  rather  than  toward  it.  When  the  arch  is  approxi- 
mately two-thirds  completed,  a  trial  ring  should  be  laid  to  determine  whether  the 
key  course  will  fit.  When  some  cutting  is  necessary  to  secure  such  a  fit,  it 
should  be  done  on  the  two  adjacent  courses  on  the  side  of  the  brick  away  from 
the  key.  It  is  necessary  that  the  keying  course  be  a  true  fit  from  top  to  bottom, 
and  after  it  has  been  dipped  and  driven  it  should  not  extend  below  the  surface 
of  the  arch,  but  preferably  should  have  its  lower  edge  ^  inch  above  this 
surface.  After  fitting,  the  keys  should  be  dipped,  replaced  loosely,  and  the 
whole  course  driven  uniformly  into  place  by  means  of  a  heavy  hammer  and 
a  piece  of  wood  extending  the  full  length  of  the  keying  course.  Such  a  driving 
in  of  this  course  should  raise  the  arch  as  a  whole  from  the  center.  The  center 
should  be  so  constructed  that  it  may  be  dropped  free  of  the  arch  when  the  key 
course  is  in  place  and  removed  from  the  furnace  without  being  burned  out. 

RELATION  OF  DRAFT  TO  SETTING  BRICKWORK — The  bearing  that  the 
draft  available  has  upon  the  boiler  setting  and  particularly  the  furnace  setting  is 
a  factor  that,  in  general,  has  only  recently  been  given  its  proper  consideration. 
Such  a  relation  is  to  be  distinguished  from  that  of  draft  and  combustion  rates. 

The  draft  available  should  be  such  as  to  provide  a  suction  throughout  all 
parts  of  the  boiler  setting  at  all  times  and  under  all  conditions  of  operation. 

35 


Where  such  a  suction  does  not  exist  and  a  back  pressure  is  found  at  any  point 
in  the  setting,  there  is  a  tendency  to  force  the  gases  of  combustion  outward 
through  the  boiler  setting  and  to  overheat  the  brickwork  and  access  and  inspec- 
tion doors.  This  overheating,  which  will  increase  as  the  gases  are  hotter  or  as 
the  boiler  furnace  is  approached,  will  naturally  cause  a  rapid  deterioration  of  the 
setting  and  warping  of  the  doors  and  frames.  Where  the  products  of  combustion 
are  not  carried  away  from  the  boiler  furnace  and  through  the  setting  by  an  ample 
draft  suction,  the  cost  of  upkeep  of  the  setting  will  be  excessive  and  will 
be  greatest  where  such  a  suction  does  not  exist  in  the  boiler  furnace.  Here  the 
highest  temperatures  are  found  and  if  the  hot  gases  are  not  removed  promptly, 
the  "soaking  up"  of  the  heat  by  the  furnace  walls  and  arches  cannot  but  be 
harmful  from  the  standpoint  of  length  of  life. 

With  a  natural  draft  stoker,  the  fact  that  there  is  sufficient  draft  in  the 
furnace  to  burn  the  necessary  amount  of  coal  to  develop  the  rating  at  which  a 
boiler  is  being  operated  is  ordinarily  a  safe  indication  that  there  is  a  draft  suction 
throughout  all  parts  of  the  setting  and  that  the  gases  are  being  properly  carried 
away  from  the  furnace.  This  statement,  of  course,  refers  to  those  instances  in 
which  there  is  no  undue  loss  in  draft  in  passing  from  the  furnace  proper  to  the 
point  at  which  the  gases  encounter  the  boiler  heating  surface. 

With  forced  draft  stokers,  on  the  other  hand,  the  blast  is  ordinarily  relied 
upon  to  give  the  required  combustion  rates.  With  this  class  of  apparatus, 
therefore,  the  function  of  the  stack  is  simply  to  remove  the  products  of  com- 
bustion from  the  furnace  and  it  is  in  such  cases  that  the  question  of  suction 
throughout  all  parts  of  the  setting  is  to  be  watched. 

It  may  be  readily  conceived  and,  in  fact,  the  condition  is  frequently  found  in 
practice,  that  a  draft  suction  in  the  boiler  furnace  does  not  necessarily  indicate 
that  such  a  suction  exists  throughout  all  parts  of  the  setting.  For  instance,  in 
a  boiler  with  vertical  or  semi-vertical  passes  for  the  gases,  a  suction  may  be 
found  in  the  furnace  while  at  the  top  of  such  a  pass  a  slight  back  pressure  may 
exist.  Such  condition  is  due  to  the  effect  of  the  column  of  heated  gases  passing 
upward,  which  acts  in  the  same  way  as  the  gases  in  a  chimney,  insofar  as 
providing  a  draft  at  the  bottom  is  concerned. 

In  determining  stack  sizes  for  forced  draft  stokers  as  for  all  boiler  work,  the 
diameter  is  a  function  of  the  amount  of  gases  to  be  handled  and  should  be  made 
such  as  to  give  no  undue  frictional  resistance  to  the  gases  because  of  insufficient 
area.  The  height  is  purely  a  function  of  the  draft  that  must  be  supplied.  With 
natural  draft  stokers,  as  with  hand  firing,  it  must  be  sufficient  to  provide  in  the 
boiler  furnace  ample  draft  to  give  the  combustion  rate  necessary  to  develop 
the  maximum  capacity  at  which  the  boiler  is  to  be  operated,  proper  attention 
being  given  to  losses  in  draft  due  to  length  of  flues,  turns,  resistance  offered  in 
the  passage  through  the  boiler,  etc. 

With  forced  draft  stokers  the  stack  height  must  be  such  that  a  draft  suction 
is  assured  throughout  all  portions  of  the  setting  under  all  conditions  of  operation, 

37 


*+-«         s 


M    H 

S    H 
0 


regardless  of  the  intensity  of  the  blast  supplied  to  give  the  necessary  combustion 
rates,  and  the  same  attention  must  be  given  to  factors  causing  draft  losses. 

In  the  early  days  of  forced  draft  stoker  work,  manufacturers  of  this  class  of 
apparatus  had  a  tendency  to  overcarry  the  mark  as  far  as  the  reduction  in  stack 
sizes  was  concerned,  taking  a  stand  that  their  product  required  practically  no 
stack.  The  importance  of  furnace  and  setting  upkeep  cost,  however,  is  now 
appreciated  by  such  manufacturers  and  they  are  insisting  that  sufficient  stack  be 
provided  to  maintain  a  draft  suction  through  the  boiler  under  all  conditions. 


Fig.  i  shows  graphically  the  draft  required  in  the  boiler  furnace  to  give 
different  combustion  rates  with  the  various  coals  which  chain  grate  stokers 
handle  with  the  most  satisfactory  results. 


39 


<  a 

5- 

0  o 

XM 

o  o 


8° 

u  c^ 


B  O 
en  53 

2 


U 


40 


TESTS    OF    VARIOUS    BOILERS    EQUIPPED    WITH 
BABCOCK  &  WILCOX  CHAIN  GRATE  STOKERS 


Plant      ..... 

Commonwealth 
Edison  Co. 

Chicago,  111. 

B.  &  W. 

5080 
508 
90 

Illinois 
Carterville 

7 

184 
127.1 
1  80 
!-2393 

.68 
i-'S 
610 

213535 
264635 

37805 

7-43 
1095.8 
215-7 
30610 

I  1.  12 

27206 
14.7 
23198 

43.20 

10.4 
9-4 

O.2 

Ross  Pumping 
Station 

Pittsburgh,  Pa. 
A.  &  T. 

35°3 
35° 
75 
Pennsylvania 
Pittsburgh 

12 

151.8 
161.3 

1  .0985 

•41 
440 

M575I 
160107 

13342 

3.81 

386.7 
1  10.5 

17850 

5-74 
16825 
17.78 
U833 

18.70 

9.8 

8.8 

O.2 

3I-38 

56.29 

'2-33 
13089 

9.52 
70.6 

Atlas  Portland 
Cement  Co. 

N'hampton,  Pa. 

B.  &  \V. 
2666 
267 
651 
Pennsylvania 
Beech  Creek 

7 

170 
127 

1-1355 

•37 
527 
56228 
63847 

9121 

3-42 

264.2 
98.9 

6716 
2.90 
6521 
14.66 
55-64 

I4-31 

30.67 
57.00 
12-33 
13547 

9-79 
70.1 

Kind  of  boiler     ....            . 

Boiler  heating  surface                                               sc].  ft. 

Rated  horse  power                                                     H.  P. 

Grate  surface      .          .     .                                       **cj.  ft. 

Bituminous  coal  from  

Mine  or  trade  name     

Duration  of  test       

hours 

Ibs. 
°F. 
°F. 

Steam  pressure  by  gauge      

Temperature  of  feed  water  

Degrees  of  superheat  

Factor  of  evaporation  

Blast  under  grates  ... 

inches 
inches 
inches 

°F. 

Ibs. 
Ibs. 

Ibs. 

Ibs. 
H.  P. 

Draft  in  furnace      

Draft  at  boiler  damper     

Temperature  of  escaping  gases     

Total  water  fed  to  boiler      

Equivalent  evaporation  from  and  at  212°  . 
Equivalent  evaporation  from  and  at  212°  per 
hour  .           .     . 

Equivalent  evaporation  from  and  at  212°  per 
square  foot  of  heating  surface  per  hour. 

Horse  power  developed 

Percent  of  rated  horse  power  developed   . 
Total  coal  fired  

10 

Ibs. 

OJ 

lo 
Ibs. 

% 
Ibs. 

Ibs. 

% 
% 
% 

% 
% 
% 
B.  t.  u. 

Ibs. 

% 

Per  cent  of  moisture  in  coal      

Total  dry  coal     

Per  cent  of  ash  and  refuse    

Total  combustible  

Dry  coal  per  square  foot  of  grate  surface,  per 
hour  

|C02    .     .     .     . 
Flue  gas  analysis  .     .     .     .    -|  O    

[  CO     .... 

{Volatile  matter 
Fixed  carbon   . 
Ash    .... 

B   t  u   per  pound  of  dry  coal         .          ... 

IO.24 
I3I26 

9-73 
71.9 

Equivalent  evaporation  from  and  at  212°  per 
pound  of  dry  coal                              .          .     . 

Efficiency  of  boiler  and  furnace     .... 

TESTS    OF  VARIOUS    BOILERS    EQUIPPED  WITH 
BABCOCK  cS:  WILCOX  CHAIN  GRATE  STOKERS 


Union  El.  Lt. 

Union  El.  Lt. 

Plant      

&  Power  Co. 

&  Power  Co. 

Location     

St.  Louis,  Mo. 

St.  Louis,  Mo. 

Boiler     

B.  &  W. 

B.  &  W. 

Heating  surface  of  boiler      .     .     . 

....      sq.  ft. 

5080 

5080 

Rated  horse  power       

....      H.  P. 

508 

508 

Grate  surface      . 

....      sq.  ft. 

103-5 

103-5 

Bituminous  coal  from       .... 



St.ClairCo.,111. 

St.ClairCo.,111. 

Mine  or  trade  name     

Mascouth 

Mascouth 

Duration  of  test       

.     .     .     .      hours 

8 

8 

Steam  pressure  by  gauge 

....        Ibs. 

180 

•83 

Temperature  of  feed  water  .     .     . 

....        °F. 

46 

53 

Degrees  of  superheat       .... 

°F. 

"3 

104 

Factor  of  evaporation       .... 

1.281 

1.2725 

Blast  under  grates  

inches 

Draft  in  fu  ranee       ...... 

.     .     .     .     inches 

.62 

.60 

Draft  at  boiler  damper     .... 

inches 

1.24 

1.26 

Temperature  of  escaping  gases 

....        °F. 

523 

567 

Total  water  fed  to  boiler       .     .     . 

....        Ibs. 

>759-s4 

195088 

Equivalent  evaporation  from  and 

at  212°      .        Ibs. 

226512 

248248 

Equivalent  evaporation  from  and  at  212°  per 

hour  

....        Ibs. 

28314 

3I03' 

Equivalent  evaporation  from  and  at  212°  per 

square  foot  of  heating  surface  per  hour     .        Ibs. 

5.67 

6.1  1 

Horse  power  developed   .... 

....      H.  P. 

820.4 

899.7 

Per  cent  of  rated  horse  power  developed  .     .          % 

161.5 

177.1 

Total  coal  fired  

....        Ibs. 

32l63 

36150 

Per  cent  of  moisture  in  coal      .     . 

....          % 

13-74 

14.62 

Total  dry  coal     

....        Ibs. 

27744 

30865 

Per  cent  of  ash  and  refuse   . 

•     -     •     •         % 

Total  combustible  

....        Ibs. 

Dry  coal  per  square  foot  of  grate  surface  per 

hour  

....        Ibs. 

33-50 

37-28 

C02 

....          % 

8.7 

8.9 

Flue  gas  analysis  ....     O     . 

....          % 

10.6 

10.7 

CO 

....          % 

o.o 

O.2 

f  Volatile  matter         % 

2896 

36.50 

Proximate  analysis  dry  coal  i.  Fixed  carbon    .          % 

46.88 

4I.2O 

[Ash 

....          % 

24.16 

22.30 

B.  t.  u.  per  pound  of  dry  coal  .     . 

.     .     .     .     B.  t.  u. 

10576 

10849 

Equivalent  evaporation  from  and  at  212°  per 
pound  of  dry  coal     Ibs. 

S.i  6 

8.04 

Efficiency  of  boiler  and  furnace     . 

....         % 

74-9 

71.9 

Babe oc  k  iV 
Wilcox  Co. 

Barberton,  O. 

Stirling 

11279 

1128 

187 

Pennsylvania 
Pittsburgh 

8 

132 

109 

152 

1.2352 

1.09 
.16 

•97 
624 

499893 
617468 

77184 
6.84 


67292 
3-5° 
64937 
18.29 
53060 

43-41 

I  1.2 
8-3 

o.o 

3'-35 
52.71 

15-94 
12130 

9.51 
76.1 


43 


~"  u 
.  o 


H  fe 
W2  O 


35  CTi 

35  »5 

•<  O 

s  M 
D> 


o"  a 


gg 

33 

z;  co 

017 
£-4 


44 


TESTS    OF   VARIOUS    BOILERS    EQUIPPED    WITH 
BABCOCK  &  WILCOX  CHAIN  GRATE  STOKERS 


Plant                

Washington 

Washington 

Tiffin  Electric 

Terminal  Co. 
Washington 

Terminal  Co. 
Washington 

Co. 

Boiler     

D.  C. 
B  &  W 

D.  C. 
B  &  W 

limn,  Ohio. 
A   &  T 

Heating  surface  of  boiler  
Rated  horse  power  

sq.  ft. 
i  H  P 

4220 

4220 

3935 

sq  ft 

8c 

8c 

61 

Somerset  Co. 

°5 
Westmoreland 

Ohio 

Mine  or  trade  name      

Pa. 

Co.,  Pa. 

Duration  of  test  

8 

3 

$ 

Steam  pressure  by  gauge      

Ibs 

156  6 

i  c8  •> 

Temperature  of  feed  water    
Degrees  of  superheat    .          

°F. 
°F 

225.6 

150.- 
234-5 

75 

Factor  of  evaporation  

i  086^ 

i  0781 

i  1  8-" 

Blast  under  grates         .               

inches 

Draft  in  furnace  

inches 

•31 

Draft  at  boiler  damper           .                    ... 

•45 

.58 

•43 

Temperature  of  escaping  gases      

Of 

443 

456 

Total  water  fed  to  boiler  

'63834 

166383 

i  08688 

Equivalent  evaporation  from  and  at  212°    .     . 
Equivalent  evaporation  from  and  at  212°    per 
hour    

Ibs 

177356 

2  2  I  69 

179411 
22426 

128491 
16061 

Equivalent  evaporation  from  and  at  212°  per 
square  foot  of  heating  surface  per  hour  .     . 

Horse  power  developed    

Ibs. 

HP 

5-25 
642.6 

650.0 

4.08 
465.5 

Per  cent  of  rated  horse  power  developed    .     . 
Total  coal  fired                  

18050 

154-0 
19225 

1  16.4 
15000 

Per  cent  of  moisture  in  coal  

7.II 

8.66 

6.01 

Total  dry  coal                

Jo 

IKc 

16767 

17560 

14099 

Of 

1771 

15-47 

19.90 

Total  combustible              

h 

14843 

11294 

Dry  coal  per  square  foot  of  grate  surface  per 
hour         

Ibs 

24.46 

25.82 

27-53 

rco2  .   .   .   . 

Flue  gas  analysis                  .  \  O    

% 

1345 
5.40 

10.30 
9.19 

10.6 
94 

(  CO      .     .     .     . 

(Volatile  matter 
Fixed  carbon    . 
Ash     .     .     .     . 
B.  t.  u.  per  pound  of  dry  coal     
Equivalent  evaporation  from  and  at  2  12°  per 

% 

% 
% 
% 
B.  t.  u. 

Ibs. 

0.41 

13.58 
78.OO 
742 

I445I 

10  58 

000 

31-65 

57-71 

10.64 

13580 

IO.O2 

o.o 

33-65 
52.01 

14-34 
12131 

9.11 

Efficiency  of  boiler  and  furnace      

7I.O 

71.6 

72.8 

45 


NEWPORT    ROLLING    MILL    CO.,    NEWPORT,    KY.     BABCOCK    &    WILCOX    CHAIN 
GRATE  STOKERS  INSTALLED  WITH  1530  HORSE  POWER  OF  STIRLING  BOILERS 


46 


TESTS    OF  VARIOUS    BOILERS    EQUIPPED  WITH 
BABCOCK  &WILCOX  CHAIN  GRATE  STOKERS 


Plant 

Erie  County 

Public  Service 

Public  Service 

Electric  Co. 

Corp.  of  N.  J. 

Corp.  of  N.  J. 

Location     

Erie,  Pa. 

Marion,  N.  J. 

Marion,  N.  J. 

Kind  of  boiler     

A.  &  T. 

B.  &  W. 

B.  &  \V. 

Boiler  heating  surface       

sq.  ft. 

5080 

6000 

6000 

Rated  horse  power       

H.  P. 

508 

600 

600 

Grate  surface      

sq.  ft. 

90 

'32 

'32 

Bituminous  coal  from       

Mercer  Co.,  Pa. 

Pennsylvania 

Pennsylvania 

Mine  or  trade  name     

Taylor  Vein 

Lancashire 

Lincoln 

Duration  of  test       

hours 

8 

S 

8 

Steam  pressure  by  gauge      

Ibs. 

1  20 

2OO 

'99 

Temperature  of  feed  water  

°F. 

69.9 

57-2 

60.7 

Degrees  of  superheat  

°F. 

280.4 

171.7 

Factor  of  evaporation       

1.1888 

1.3909 

1.3191 

Blast  under  grates  

inches 

•52 

•'5 

Draft  in  furnace       

inches 

•3' 

.04. 

Draft  at  boiler  damper     

inches 

.58 

•52 

•S- 

Temperature  of  escaping  gases     

°F. 

533 

590 

529 

Total  water  fed  to  boiler       

Ibs. 

166072 

231248 

184592 

Equivalent  evaporation  from  and  at  212°  .     . 

Ibs. 

197424 

321640 

243496 

Equivalent  evaporation  from  and  at  212°  per 

hour  

Ibs. 

24678 

40205 

30437 

Equivalent  evaporation  from  and  at  212°  per 

square  foot  of  heating  surface  per  hour 

Ibs. 

4.85 

6.70 

5.07 

Horse  power  developed   

H.  P. 

7'5-3 

1  165.2 

882.0 

Per  cent  of  rated  horse  power  developed    . 

% 

140.8 

194.2 

147.0 

Total  coal  fired  

Ibs. 

22328 

32205 

24243 

Per  cent  of  moisture  in  coal      

% 

4.42 

4-03 

4.09 

Total  dry  coal     

Ibs. 

21341 

30907 

23251 

Per  cent  of  ash  and  refuse    

% 

1  6.88 

15.65 

12.33 

Total  combustible  

Ibs. 

17739 

26070 

20385 

Dry  coal  per  square  foot  of  grate  surface  per 

hour  

Ibs. 

29.64 

29.26 

22.OI 

f  CO,     .     .     .     . 

% 

I  O.I 

10.5 

IO.I 

i 

Flue  gas  analysis  ....•!  O    

% 

9-i 

8-3 

9-0 

[  CO      .... 

/o 

o.o 

o.o 

O.O 

f  Volatile   matter 

% 

33-26 

22.84 

32-36 

Proximate  analysis  dry  coal  •!  Fixed  carbon    . 

% 

54-03 

69.91 

60.67 

[  Ash      .... 

% 

12.71 

7-25 

6.97 

B.  t.  u.  per  pound  of  dry  coal   

B.  t.  u 

12742 

13840 

14027 

Equivalent  evaporation  from  and  at  212°  per 

pound  of  dry  coal     

Ibs. 

9.25 

10.41 

10.47 

Efficiency  of  boiler  and  furnace     

70.4 

72.6 

72.1 

47 


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48 


COLORADO    SCHOOL    OF   MINES,   GOLDEN,   COL.     BABCOCK    &  WILCOX    CHAIN 

GRATE   STOKERS   INSTALLED  WITH   300   HORSE    POWER   OF 

BABCOCK   &  WILCOX    BOILERS 

5° 


ERIE    COUNTY    ELECTRIC    CO.,    ERIE,    PA.      OPERATING    BABCOCK    &    WILCOX 

CHAIN    GRATE    STOKERS    IN    CONNECTION  WITH   3100   HORSE    POWER 

OF    BABCOCK    &  WILCOX    BOILERS 

5' 


PETER    SCHOENHOFEN    BREWING    CO.,   CHICAGO,    ILL.      BABCOCK    &    WILCOX 

CHAIN    GRATE   STOKERS    INSTALLED  WITH   2(500   HORSE    POWER 

OF   BABCOCK   &    WILCOX    BOILERS 

52 


SOUTH    SIDE   ELEVATED   RY.  CO.,   CHICAGO,  ILL.     BABCOCK  &  WILCOX  CHAIN 

GRATE   STOKERS    INSTALLED  WITH   JJJKX)   HORSE    POWER   OF 

BABCOCK   &  WILCOX    BOILERS 


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